1. Field of the Invention
This invention relates to guidewires for use in biological conduits. More particularly this invention relates to guidewires which are articulated for rotating a sensor.
2. Previous Art
Atherosclerosis, a common vascular disease, is characterized by undesired deposits of material on the interior of an artery. These deposits include atheroma which is formed from a range of matter from soft fatty material to hard calcified tissue. Atheroma may occlude the artery and restrict blood flow. In some cases, restricted blood flow causes severe complications including strokes and heart attacks.
Recently, much research focuses on treatments for atherosclerosis. One successful treatment is a surgical procedure known as atherectomy. Atherectomy procedures generally restore blood flow in occluded arteries by reducing the size of atheroma. During an atherectomy, a catheter is inserted into the vasculature through an incision made, for example, in the femoral artery of a patient. The catheter slides through the vasculature of a patient to an occluded region where an atheroma is formed.
A small cutter is disposed within the atherectomy catheter. When the catheter is properly inserted into the vasculature, the cutter aligns with an atheroma. The cutter rotates and translates, removing the atheroma in small pieces. The catheter retains the small pieces. Removal of the catheter with the small pieces of atheroma completes the atherectomy procedure. An example of the atherectomy catheter is disclosed by Gifford III et al. in U.S. Pat. No. 5,071,425, the disclosure of which is incorporated herein by reference.
Undesirable deposits (e.g. deposits which cause occlusion) may also form in various biological conduits such as within the urinary tract. Devices and techniques used for atherectomy procedures are adapted in size, flexibility and operation to remove the undesirable deposits from various biological conduits. For example, work elements such as cutters, sensors and other diagnostic devices can be adapted for specific use in various biological conduits.
The location of an occlusion in a biological conduit must be precisely identified. This is accomplished through various diagnostic techniques such as fluoroscopy. With the location of an undesirable deposit identified, a guidewire is inserted into the biological conduit. In the case of atherectomy, for example, the guidewire inserts into the vasculature via the femoral artery. The guidewire slides through the biological conduit to a position distal the undesirable deposit (e.g. atheroma). With the guidewire in place, the catheter device is inserted into the biological conduit over the guidewire and follows the path of the guidewire by tracking over the guidewire. The catheter tracks over the guidewire until the cutter of the catheter aligns with the undesirable deposit.
Precise positioning of the catheter in the vasculature is necessary to perform an atherectomy. To facilitate precise positioning, some catheter devices include a sensor. The catheter moves within the vasculature until the sensor detects the location of the atheroma which is desired to be removed.
A sensor may be mounted on the work element or other part of the catheter device, for example. During use, the sensor typically determines the exact location of the catheter device relative to an undesired deposit. The sensor may also determine characteristics such as the geometry and density of an undesirable deposit which is to be removed. The sensors communicate such characteristics via the catheter device to a display system. An operator (i.e., surgeon) then relies upon the display system to properly align the catheter with the undesired deposit. An example of an atherectomy catheter which employs a sensor mounted on a cutter is described by Leary et al. in U.S. Pat. No. 5,024,234, the disclosure of which is incorporated herein by reference.
The vasculature is often sensitive to catheter insertion. Catheters having a work element and a sensor may have a relatively large diameter which may injure the interior of a blood vessel. In rare cases, a risk of injury to a patient is needlessly created when a surgeon inserts an atherectomy catheter with a sensor into a patient only to find that an atherectomy is not necessary to perform. Accordingly, it is desired to operate a sensor independently of a catheter device so that a determination as to the necessity of removing deposits from an occluded blood vessel can be made prior to insertion of the catheter device into the vasculature. What is also desired is a way of precisely positioning a guidewire within a biological conduit to facilitate precise insertion of a catheter device. What is also desired is a way to monitor the effectiveness of an atherectomy procedure after an atherectomy catheter is removed.